Automatic Packaging Method

ABSTRACT

A film extruding mechanism for melting and extruding a resin material as raw material of a film to be formed from a resin extruding outlet so as to form the film using extrusion technology is disposed adjacent to a tray that contains an article to be packaging. The article to be packaged is packaged as soon as the film is formed while the film extruding mechanism forms the film. Accordingly, the article to be packaged can be easily packaged without preparation of the film.

BACK GROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an automatic packaging method and an automatic packaging apparatus for packaging an article to be packaged with a film formed by resin material.

[0003] 2. Description of the Prior Art

[0004] Heretofore, a plastic tray with a plastic cover is generally used for containing foods in grocery store, drug store, food court or something like that. These plastic trays and covers are formed by plastic forming apparatus in succession, so that these are suitable for mass production. Generally, these plastic trays and covers are formed with certain form by die forming using a plastic blank material.

[0005] However, above-mentioned plastic forming apparatus requires own mold for each plastic product having different form. Therefore, plural sizes of molds are required if plural sizes of trays and the covers are requested, so that use and maintenance of the molds is troublesome.

[0006] Stretch packaging method is also usually used for containing foods. This type of packaging method can eliminate above drawback concerning the plastic forming technique. Japanese un-examined publication document no. hei 8-217008 and Japanese un-examined publication document no. hei 9-12004 introduce a stretch packaging apparatus for packaging an article using a stretching film. This type of apparatus automatically selects preset film size according to the tray size fed from an article feed unit, and packages the article with the film fed from a film unit.

[0007] However, this type of packaging method requires many amount of stock of a roll film. The stretch packaging apparatus is able to package the article being suitable of several sizes of the trays, which contains the article. Thus, several widths of roll films for packaging the article should be prepared in advance.

[0008] The stretch packaging apparatus has other drawback. The thickness of stretch film is usually uneven and some portions of the stretch film is usually very thin because the stretch film is formed by stretching the film having constant thickness so as to be suitable of the tray size. Thus, the stretch film often tears at thin portions. Also, the stretch film is not strong in nature. The stretch film is not suitable for the articles having projections, thorns or spines.

SUMMARY OF THE INVENTION

[0009] Accordingly, an object of the present invention is to provide an automatic packaging method and an automatic packaging apparatus to be capable of packaging an article without preparation of rolls of film.

[0010] Another object of the present invention is to provide an automatic packaging method and an automatic packaging apparatus to be capable of packaging the article using minimum amount of film material.

[0011] Another object of the present invention is to provide an automatic packaging method and an automatic packaging apparatus to be capable of forming the film with various kinds of width and thickness.

[0012] A further object of the present invention is to provide an automatic packaging method and an automatic packaging apparatus to be capable of forming the film without preparing a roll film previously.

[0013] These and further objects of the present invention are achieved by the novel automatic packaging method and automatic packaging apparatus of the present invention.

[0014] According to the present invention there is provided an automatic packaging method wherein melted resin material as raw material of a film is extruding from a resin extruding outlet, extruded resin is cooled so as to form the film, the film is immediately introduced after forming the film above a tray charged with an article to be packaged, and the article is packaged with the film. Accordingly, the article can be packaged without preparing a roll film previously because the article is packaged while the film is formed.

[0015] Another aspect of the present invention there is provided an automatic packaging method wherein a tray, which contains an article to be packaged, is positioned adjacent to a film extruding mechanism for extruding melted resin material as raw material of a film from a resin extruding outlet so as to form the film; and the article is packaged with the film while the film extruding mechanism forms the film. Accordingly, the article can be packaged without preparing a roll film previously because the article is packaged while the film is formed.

[0016] Another aspect of the present invention there is provided an automatic packaging apparatus comprises a film extruding mechanism for extruding melted resin material as raw material of a film from a resin extruding outlet, a film forming mechanism for touching the extruded resin with a surface of rotating cooling drum so as to cool and solidify the extruded resin from the resin extruding outlet, and a packaging mechanism for introducing the film immediately, after solidifying on the surface of cooling drum, above a tray charged with an article to be packaged to package the article with the film. Accordingly necessary film for packaging the article can be formed when the article is packaged so that film forming operation and article packaging operation can be done easily with same apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which:

[0018]FIG. 1 is a perspective view showing an inner structure of a packaging apparatus according to an embodiment of the present invention;

[0019]FIG. 2 is a longitudinal sectional view showing the inner structure of the packaging apparatus;

[0020]FIG. 3 is a longitudinal sectional view of a film extruding mechanism;

[0021]FIG. 4 is a front view showing the inner structure of the packaging apparatus;

[0022]FIG. 5 is a perspective view of a scraper;

[0023]FIG. 6 is a perspective view of a mechanism for adjusting thickness of the film;

[0024]FIG. 7 is a longitudinal sectional view thereof;

[0025]FIG. 8 is a perspective view of a mechanism for adjusting width of the film;

[0026]FIG. 9 is a perspective view of a packaging apparatus according to other embodiment of the present invention;

[0027]FIG. 10 is a front view of a tray with film drawn out above the tray;

[0028]FIG. 11 is a front view of the tray with film positioned on the tray;

[0029]FIG. 12 is a front view of the tray with film portions overhanging from the tray pulled down sideways of the tray;

[0030]FIG. 13 is a perspective view of the tray with film positioned on the tray;

[0031]FIG. 14 is a perspective view of the tray with film positioned on the tray and spread;

[0032]FIG. 15 is a front view of the tray with film started to converge under the jet of hot air;

[0033]FIG. 16 is a front view of the tray with a solid edge portion formed by film;

[0034]FIG. 17 is a perspective view of a packaging apparatus according to other embodiment of the present invention;

[0035]FIG. 18 is a functional block diagram showing a control system;

[0036]FIG. 19 is a block diagram showing the control system;

[0037]FIG. 20 is a flow chart for film forming process and film packaging process;

[0038]FIG. 21 is a flow chart showing a subroutine executed in an input/display controller;

[0039]FIG. 22 is a flow chart showing a subroutine executed in a packaging controller;

[0040]FIG. 23 is a flow chart showing a subroutine executed in a packaging condition setting controller;

[0041]FIG. 24 is a flow chart showing a subroutine executed in a film forming controller;

[0042]FIG. 25 is a flow chart showing a subroutine executed in the packaging controller.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] An embodiment of the present invention is now explained with reference to FIGS. 1 to 8. FIG. 1 shows basic structure of an automatic packaging apparatus in this embodiment. A detail of the same is mentioned below. An packaging machine 1 as the automatic packaging apparatus 201 includes uniformly a film unit 205 for forming a film 15 and a packaging unit 202 for sealing an upper surface of a tray 2 with the film 15. The packaging machine 1 has a tray table 3 for supporting the tray 2 containing an article to be packaged. A film forming unit 4 is provide above the tray table 3. The film forming unit 4 contains a linear actuator 5 for raising and lowering the film unit 205 according to a height of the tray 2 set on the tray table 3, a pair of linear actuators 7 provided along a seal surface 6 of the tray 2 and a pair of linear guide rail 8 for guiding the linear actuator 7. Such arrangement of each member, the linear actuator 5 and the linear actuator 7 operate as a packaging mechanism 51 for packaging the tray 2. Especially, the linear actuator 5 also operates as rising/lowering mechanism 52 for rising and lowering the film forming unit 4. A block diagram of FIG. 19 shows the linear actuator 5 and the linear actuator 7 as an actuator Act.

[0044] The film forming unit 4 and an extruding unit 101 will be explained with reference to FIGS. 2 and 3. The extruding unit 101 feeds heated and melted pellet into the film forming unit 4. These film forming unit 4 and the extruding unit 101 comprises a film extruding mechanism 13. The pellet, ethylene vinyl acetate copolymer for instance, is used for a film material. Thermo plastic synthetic resin, polyethylene, polypropylene or nylon for instance, also can be used for the film material. The film extruding unit 101 heats and melts the pellet with 170-200° C. to feed the melted pellet into a resin extruding portion 9 by pressure means. The extruding unit 101 has a housing 102 including a mandrel 103, which feeds the melted pellet into the resin extruding portion 9 by rotation thereof. The housing 102 has a hopper 104 for introducing the pellet into a pellet transfer space of the mandrel 103. The housing 102 also has a heater 105, built-in it, for heating a solid pellet or the melted resin and keeping the resin in melted condition. The extruding unit 101 rotates the mandrel 103 by a motor M shown in FIG. 19 so that the mandrel 103 forwards the pellet with a screw 106 formed on a surface of the mandrel 103 while the mandrel 103 stirs the pellet. For other embodiment, pressure means for feeding the pellet into the resin extruding portion 9 of the extruding unit 101 may be used other structure such as a pressure pump.

[0045] The resin extruding portion 9 provided in the film forming unit 4 comprises a resin feed tube 10. The resin feed tube 10 comprises a flexible pipe 11 formed by stainless steel for instance, and a heat insulating material 12 for covering a periphery of the flexible tube 11. A nozzle 14 as a resin extruding outlet is provide. The nozzle 14 feeds the melted resin to a cooling drum 16 while a mechanism for controlling a thickness and width of the film 15 sets a gap and width of the nozzle 14 with desired value. For concrete value with respect to the thickness of the film 15, 30 μm-100 μm are set so as to be suitable for packaging of the article to be packaged. The surface of the cooling drum 16 is cooled by cooling system, coolant around 20° C. for instance, when the melted resin has been fed to the cooling drum 16. The cooling drum 16 has a hollow 17. The cooling drum 16 is formed by machining using SUS 630. A pair of hollow supporting shafts 18 is provided at both ends of the cooling drum 16 as shown in FIG. 4. These supporting shafts 18 are attached on a supporting frame 19 via a pair of bearings 20. A pair of pipes 22 as a passage of coolant 23 connects to the hollow supporting shafts 18 via a pair of rotary joint 21. The coolant 23 can be introduced into the cooling drum 16 through one of the pipes 22, rotary joints 21 and supporting shafts 18 as shown in FIG. 1. A coolant liquid such as a coolant water and coolant air can be used as the coolant 23.

[0046] A film forming mechanism 24 comprises the cooling drum 16, periphery mechanisms thereof, and the arrangement between the film extruding mechanism 13 and the cooling drum 16. The periphery mechanisms of the cooling drum 16 include a driving mechanism for rotating the cooling drum 16. The driving mechanism comprises a motor 26 supported on the supporting frame 19, and transmission gears 27 for transmitting a driving power from the motor 26 to the cooling drum 16. The motor 26 is shown as the motor M in FIG. 19. The melted resin extruding from the nozzle 14 is cooled by touch on the surface of the cooling drum 16, so that the melted resin becomes the film 15. The cooling drum 16 rotates when the melted resin has been extruded from the nozzle 14, so that an front end of the film 15 on the surface of the cooling drum 16 feeds to the scraper 25. Thus, the scraper 25 peels the front end of the film 15 from the cooling drum 16 when the front end of the film 15 was reached at the scraper 25.

[0047] The packaging mechanism 51 will be explained. The linear actuator 7 drives the film unit 205 while the above-mentioned film forming operation has been done, so that the film unit 205 moves along the tray 2 on the tray table 3 in arrow direction of FIG. 2. The movement of the film unit 205 synchronizes the rotation of the cooling drum 16, so that the peeled film 15 drops on the seal surface 6 of the tray 2. In this embodiment, the seal surface 6 has adhesive so as to adhere the film 15 to the seal surface 6. The width of the film 15 can be easily suitable for the width of the tray 2 by the above-mentioned mechanism for controlling the thickness and width of the film 15. This mechanism includes a pair of slidable obstructing member 36 disposed at both sides in the nozzle 14 as mentioned below. The packaging mechanism 51 is able to be suitable for several height of the tray 2 because, as mentioned above, the linear actuator 5 raises and lowers the film unit 205 according to the height of the tray 2 on the tray table 3.

[0048] The cooling system using the cooling drum 16 will be explained. The coolant 23 can be introduced into the cooling drum 16 through one of the pipes 22, rotary joints 21 and one end of the supporting shafts 18 as shown in FIG. 1, so that the surface of the cooling drum 16 is cooled. The warmed coolant 23 in the cooling drum 16 drains through other end of the supporting shaft 18. There is provided a temperature sensor (not shown) for detecting a temperature of the cooling drum 16. In this embodiment, the flow rate of the coolant 23 can be adjusted according to detected temperature value of the sensor, so that the temperature on the surface of the cooling drum 16 can be kept in certain temperature.

[0049] In this embodiment, the nozzle 14 of the resin extruding portion 9 is arranged upward, disposed toward the cooling drum 16 with little gap, and inclined, so that the nozzle 14 is positioned at upper position more than an axis of the cooling drum 16. Thus, the melted resin from the nozzle 14 can be touched as soon as the melted resin is extruded from the nozzle 14, so that the thickness of the film 15 can be kept in constant.

[0050] The film 15 on the cooling drum 16 can be easily peeled. This is because the surface of the cooling drum 16 has fluoro resin treatment. Also, the scraper 25 touches the peripheral surface of the cooling drum 16 with its acute-angled edge portion at film peeling point with certain angle. For other embodiment, the scraper 25 may be disposed toward the cooling drum with little gap. The scraper 25 is preferably made by fluoro resin material whose peeling characteristics with film 15 are well. For other embodiment, fruoro resin may be treated on the surface of the metal scraper 25.

[0051] Pealing characteristics can be improved by adding micro-vibration to the scraper 25. FIG. 5 shows a scraper supporting structure with means for driving the scraper 25 so as to arise the micro-vibration. As shown in FIG. 5, the pair of supporting frames 19, for supporting the supporting shafts 18 of the cooling drum 16 (refer FIG. 4), have a pair of fixing seats 107. There are provided a pair of scraper holder 109 for holding both ends of the scraper 25. The scraper holders 109 are attached to the fixing seats 107 via a pair of leaf springs 108. A pair of piezoelectric elements 110 is attached on the leaf springs 108. Poly vinyliden fluoride (PVDF) for instance is used for the piezoelectric elements 110. A length of the scraper 25 is set as two leaf springs 108 urges preload each other in static condition. Thus, the piezoelectric elements 110 strain by supplying voltage, so that one of the leaf springs 108 is deflects toward the other one of the leaf springs 108. Accordingly, the micro-vibration can be arose in the scraper 25 by applying the alternative voltage to the piezoelectric elements 110 frequently.

[0052] The driving source for giving micro-vibration in the scraper 25 is not limited as the piezoelectric elements 110. Electric strain elements for instance may be used.

[0053] The film 15 should have certain rigidity for keeping its form when the film 15 is peeled from the cooling drum 16 because the film 15 is formed by cooling process of the melted resin extruded from the nozzle 14 to the cooling drum 16 with certain width and thickness. However, cooling process completes depending on the width and thickness of the film 15. Thus, in this embodiment, the velocity of the cooling drum 16 can be adjusted, so that the cooling period for cooling process can be controlled.

[0054] An obstructing plate driving mechanism will be explained with reference to FIGS. 6 to 8. There is provided an obstructing plate 29 at the nozzle 14. The obstructing plate 29 has a width, which is longer than maximum width of the nozzle 14. As shown in FIGS. 6 and 7, the obstructing plate 29 is attached slidable in the nozzle 14. The obstructing plate 29 is urged in a direction so as to shut the nozzle 14 by a pair of springs 30 at both ends thereof. An ellipse opening 31 is formed around center portion of the obstructing plate 29. An eccentric cam 33 driven by a motor 32 is disposed at the ellipse opening 31, so that the Scotch yoke mechanism is formed. Thus, the obstructing plate 29 can be raised and lowered by rotation of the eccentric cam 33 driven by the motor 32 so as to adjusting the gap of the nozzle 14. Then, the extruding amount of the melted resin from the nozzle 14 is adjusted, so that the thickness of the film 15 can be controlled.

[0055] As other method for controlling the thickness of the film 15, the velocity of the cooling drum 16 can be adjusted.

[0056] A mechanism for adjusting the width of the film 15 will be explained with reference to FIGS. 4, 7 and 8. The width of the film 15 should be adjusted according to a size or kind of the tray 2. As shown in FIGS. 4 and 8, a pair of linear actuator 34 is fixed to the pair of supporting plates 19. As described above, the pair of obstructing members 36 is disposed in the nozzle 14 as showing in FIG. 7. Each linear actuator 34 and the obstructing member 36 are connected with connecting plate 37. This is a basic structure of the mechanism for adjusting the width of the film 15. An interval of the ends of the obstructing members 36 determines effective nozzle width because the obstructing members 36 cover the opening of the nozzle 14 completely. Thus, the melted resin can be merely extruded from the effective nozzle width. As shown in FIG. 8, each linear actuator 34 for driving the obstructing member 14 includes linear actuator shaft 35 having screw on its periphery and guide shaft 112 having smoothness on its periphery. Each linear actuator shaft 35 and guide shaft 112 are movably contained in an actuator housing 111. Each linear actuator shaft 35 and guide shaft 112 are connected to the obstructing members 36 via the connecting plate 37. Each linear actuator shaft 35 is mounted at the connecting plate 37. There is provided a floating nut (not shown) driven by the motor M shown in FIG. 19 in each actuator housing 111. Each floating nut transmits rotation power from the motor M to the linear actuator shaft 35 so as to rotate the linear actuator shaft 35. Each linear actuator shaft 35 moves right or left direction according to the rotation of each floating nuts, so that each obstructing member 36 slides in the nozzle 14 with the linear actuator shaft 35. Thus, the interval of the ends of the obstructing members 36 can be adjusted, so that the width of the film 15 can be controlled. That is, it is possible to form the film 15 having a size being suitable for the tray 2 and the article to be packaged.

[0057] A film forming process will be explained below.

[0058] The film forming process of the present invention is similar to conventional extrusion technique. However, the pellet amount for one extrusion is very little. And the pellet, which became the melted resin, is not extruded continuously. These features identify the extruding method used in the present invention from the conventional extrusion technique. These features contribute compactness of the apparatus, so that the film unit 205 can be built into the automatic packaging apparatus 201.

[0059] As mentioned above, the extruding unit 101 drives the mandrel 103 by the motor M, and forwards the pellet with the screw 106 formed on the periphery surface of the mandrel 103 while the mandrel 103 stirs the pellet. Then, the nozzle 14 provided in the film forming unit 4 is filled with the pellet, which became the melted resin, so that preparation for film forming completes. After the preparation of it, the mandrel 103 is forward and backward driven so as to keep the end position of the melted resin in the nozzle 14. This is named waiting condition. The film forming unit 4 starts up the film forming operation according to start up signal from the automatic packaging apparatus 201. After starting up, the cooling drum 16 is driven by the motor 26 to rotate. The mandrel 103 is also driven by the motor M as shown in FIG. 19 to rotate, so that the melted resin is extruded from the nozzle 14. Extruded resin is cooled by the touch to the periphery surface of the cooling drum 16, so that the melted resin solidifies and becomes the film 15. The film 15 is fed to left direction in FIG. 3 so as to be peeled from the cooling drum 16 by the scraper 25. Peeled film 15 can be handled as ordinary film. A film forming controller 301, shown in FIG. 18, watches rotary operation of the mandrel 103. The film forming controller 301 rapidly drives the motor M for the mandrel 103 backward when the film forming controller 301 determines that enough amount of the melted resin for the film 15 to be formed is extruded from the nozzle 14. Then, the mandrel 103 is rapidly driven backward. Thus, the supply of the melted resin to the nozzle 14 is rapidly broken off, so that the last end of the film 15 on the cooling drum 16 is also separated from the melted resin. The melted resin is drawn back into the nozzle 14 uniformly in the width direction thereof because the nozzle 14 is disposed upward. Thus, the straightness at last end of the film 15, as well as at front end of the next film to be formed, can be improved.

[0060] Next, whole process of the packaging operation will be described.

[0061] (1) Keep the pellet as resin material for the film 15 in heated and melted condition with certain temperature.

[0062] (2) Set the tray 2 charged with the article to be packaged on the tray table 3 at standard position for packaging. It is preferable to obtain size of the tray 2 by measuring the size using a sensor S, an optical sensor or image-processing sensor for instance (refer FIG. 19). The size data to be obtained is used as a basic data for determining the width and the thickness of the film 15 to be formed.

[0063] (3) Start up the mandrel 103 for obtaining waiting condition. Heated and melted resin material is extruded into the nozzle 14 and kept in the nozzle 14.

[0064] (4) Move the film unit 205 to a packaging start up position. The packaging start up position is adjacent to the standard position. It is preferable to return the film unit 205 at the packaging start up position after one cycle of the packaging operation because the packaging start up position identifies the starting point. Then, dispose the film unit 205 at certain height by driving the linear actuator 5.

[0065] (5) Determine the width of the film 15 to be formed, by moving the obstructing members 36, according to the measured data of the tray 2. The linear actuator 34 can move the obstructing members 36 via the connecting plate 37. The obstructing members 36 at right side and left side can be moved toward inner side and outer side in certain amount. Thus, the width of the film 15 is determined as center standard.

[0066] (6) Drive the cooling drum 16. Adjust the thickness of the film 15 by driving the eccentric cam 33. The eccentric cam 33 drives the obstructing plated 29.

[0067] (7) The cooling drum 16 is kept cool because the coolant 23 is introduced to the hollow 17 of the cooling drum 16 via the pipe 22 and rotary joint 21. The extruded resin touches the periphery surface of the cooling drum 16, so that the heated and melted resin is cooled to become the film 15 having certain rigidity for keeping its form. The film 15 is fed to the standard position for packaging.

[0068] (8) The scraper 25 having sharp edge is disposed at opposite side of the resin extruding portion 9 with width longer than the width of the film 15 in order to peel the film 15 easily from the cooling drum 16. The film 15 on the periphery surface of the cooling drum 16 is effectively peeled from the cooling drum 16 by micro-vibration of the scraper 25.

[0069] (9) The film unit 205 is controlled so as to move opposite direction to the standard position by the pair of linear guide rails 8 and the pair of linear actuators 7 while the film unit 205 executes above (5)-(8) processes.

[0070] (10) Formed film 15 moves while the film 15 touches the seal surface 6 of the tray 2. It is possible to seal the film 15 strongly to the tray 2 when a moving roller (not shown) for instance put pressure on the tray 2. In this case, the actuator Act shown in FIG. 19 drives the moving roller.

[0071] (11) The film unit 205 moves upward or downward, while the film unit 205 moves packaging direction, by driving the linear actuator 5 depending on the height of the article to be contained in the tray 2. The width of the film 15 also can be adjusted according to the moving amount of the film unit 205. In such case, the film 15 having different width through its forming direction is issued.

[0072] (12) The resin supply is rapidly stopped and the obstructing plate 29 is rapidly shut after forming the film 15 and packaging, so that the extruding unit 101 stops extruding the resin completely.

[0073] (13) Move the film unit 205 upward and stop the same. Then, the packaged tray 2 can be removed from the tray table 3.

[0074] (14) One cycle of the packaging process has been ended.

[0075] Other embodiment of the present invention is now explained with reference to FIGS. 9 to 16. The same parts as those in the former embodiment are designated by the same reference numerals, and are not again explained herein. This embodiment relates to the automatic packaging apparatus 201 which packages the article to be packaged automatically after forming the film 15. The former embodiment introduces the automatic packaging apparatus 201, which drops the forming film 15 from the cooling drum 16 on the seal surface 6 of the tray 2 so as to adhere the film 15 to the seal surface 6 of the tray 2. The former embodiment also introduces the pressure roller, which puts pressure on the tray 2 for seal the film 15 to the tray 2 strongly. This embodiment will introduce automatic packaging apparatus 201 of which film grippers 207 grips the film 15 extruded by the film forming unit 4 for packaging operation. More specifically, the film grippers 207 feed the film 15 above the tray 2 disposed in the packaging unit 202, and move the film 15 downward so as to dispose the gripping position of the film 15 lower than the upper surface of the tray 2. Then, packaging operation is executed by heating the edge portion of the film 15. The detail description of this embodiment is now explained below.

[0076] What is illustrated in FIG. 9 is the automatic packaging apparatus 201. The automatic packaging apparatus 201 comprises the packaging unit 202, a tray feed unit 203 and a tray discharge unit 204 disposed on the left and right sides, respectively, of the packaging unit 202, and the film unit 205 disposed behind the packaging unit 202. With this arrangement, the automatic packaging apparatus 201 can package continuously a large number of articles to be packaged. The tray feed unit 203 feeds a tray 2 to the packaging unit 202 in a continuous manner, the tray discharge unit 204 discharges the tray 2 after packaged, and the film unit 205 feeds the film 15 to the packaging unit 202 in a successive manner. As to detailed structures of the tray feed unit 203 and tray discharge unit 204, explanations thereof are here omitted. The detailed structure of the film unit 205 is substantially the same as the former embodiment, so that explanations thereof are also here omitted.

[0077] The packaging unit 202 is provided with a tray table 3 on which the tray 2 is placed. Four blowers 206, whose heaters H are built in it, are arranged so as to surround four sides of the tray 2 put on the tray table 3. Also mounted are four film grippers 207 (only two are shown in FIG. 9) for gripping four corners of the film 15 pulled out from the film unit 205.

[0078] The tray 2 is formed with an upper opening 209 having a peripheral fitting edge 208 and is in the shape of an upwardly expanded tray as a whole.

[0079] In such a construction, as shown in FIG. 10, the tray 2 charged with an article (not shown) to be packaged is fed from the tray feed unit 203 onto the tray table 3 in the packaging unit 202 and at the same time the film 15 is fed from the film unit 205. The film 15 is gripped at four corners thereof by the film grippers 207. In this state, the film grippers 207 move down into contact with the tray 2 while pulling the film so as not to wrinkle the film, to cover the opening 209 of the tray 2, as shown in FIGS. 11 and 12. Further, as shown in FIG. 13, the film grippers 207 turn and move down, causing overhanging portions of the film 15 overhanging from the tray 2 to approach the side faces of the tray 2. At this time, as shown in FIG. 12, it is desirable that the gripping direction of the film grippers 207 is an upward direction toward the fitting edge 208.

[0080] When end portions of the film 15 have reached a position lower than the opening 209 of the tray 2 in a fully pulled state of the film 15, the blowers 206 positioned around the tray 2 are driven to blow hot air against the four sides of the container. Taking the influence on the article to be packaged into account, a jet of hot air at 120° C. for about 3 seconds is desirable. With this hot air, end portions of the film 15 become hot and shrink. As a result of this thermal shrinkage the overhanging portions of the film 15 overhanging from the tray 2 converge to enhance their rigidity and extend inside along the fitting edge 208 to form a solid edge portion 210 below the fitting edge 208. In this case, an appropriate timing for ungripping the film 15 from the gripped state by the film grippers 207 is set in synchronism with shrinkage of the film positioned at the side portions of the tray 2. The solid edge portion 210 is formed also by the four corners of the film 15. AS a result of formation of the solid edge portion 210 there is formed a cover member 18 by the film 15. The solid edge portion 210 is fitted with the fitting edge 208 of the tray 2 and is not heat-fused to the tray 2. Of course, the solid edge portion 210 may be heat-fused to the tray 2 to such an extent that it can be stripped off easily. Therefore, when the article to be packaged is to be taken out from the tray 2, a finger is put on the solid edge portion 210 and is moved in a direction to come off the fitting edge 208, whereby the film 15 is separated easily from the tray 2 and the upper surface of the tray 2 can be opened without damaging the tray 2.

[0081] Another method for pulling a film, which covers a tray 2 according to the present invention, will now be described with reference to FIG. 17. The same parts as those in the former embodiments are designated by the same reference numerals, and are not again explained herein.

[0082] What is illustrated in FIG. 17 is the automatic packaging apparatus 201 provided with the packaging unit 202 for stretching the film 15. The automatic packaging apparatus 201 comprises the tray feed unit 203 and the tray discharge unit 204 disposed on the left and right sides, respectively, of the packaging unit 202 and the film unit 205 disposed behind the packaging unit 202. According to this arrangement, a large number of articles to be packaged can be packaged in a continuous manner. The tray feed unit 203 feeds trays 2 to the packaging unit 202 continuously one by one, the tray discharge unit 204 discharges packaged trays 2, and the film unit 205 feeds the film 15 to the packaging unit 202 in a successive manner. As to detailed structures of the tray feed unit 203 and the tray discharge unit 204, explanations thereof are here omitted. The detailed structure of the film unit 205 is substantially the same as the former embodiments, so that explanations thereof are also here omitted.

[0083] The packaging unit 202 comprises the tray table 3 which includes a container raising/lowering mechanism (not shown) for moving the tray 2 up and down while carrying it thereon, film grippers 207, for drawing out the film 15 to the packaging unit 202 and gripping four corners of the film, the film grippers 207 being also used for stretching, film pulling mechanisms 211, as the film gripper, and linear-acting actuators 112. The film pulling mechanisms 211 themselves, which are provided four, can move back and forth and turn vertically and the film pulling mechanisms 211 located on the linear-acting actuators 112 which are disposed two at right and left positions can also move in the longitudinal direction of the automatic packaging apparatus 201, whereby the formed film 15 can be gripped, stretched and ungripped.

[0084] The detailed structure of the film unit 205 is substantially the same as the film unit 205 shown in FIGS. 1 to 8. A front end portion of the film 15, formed by the film unit 205, is fed to a film delivery section 213. In this case, a control is made so that the front end portion of the film is set at an initial position at which it slightly overhangs to the packaging unit 202 side with respect to the film delivery section 213.

[0085] In such a configuration, when the tray 2 charged with an article (not shown) has been fed onto the tray table 3 in the packaging unit 202, the linear-acting actuator 212 operates and two film grippers 207 located on the linear-acting actuators 112 and on the front side of the apparatus grip the film 15 overhanging from the film delivery section 213, then the film 15 is drawn out to above the tray 2. Thereafter, two film grippers 207 located at rear positions grip the film 15. The amount of the film 15 to be drawn out differs depending on the size of the tray 2 and a film forming controller 301 described below controls the film drawing-out operation (refer FIG. 18). At this time, the film pulling mechanisms 211 not concerned in drawing out the film 15 are located at positions not obstructing the drawing-out operation.

[0086] After the film 15 has been drawn out to above the tray 2, the film pulling mechanisms 211 grasp the centers in each side of the film 15, both film pulling mechanisms 211 and film grippers 207 stretches the film 15. As a result, as shown in FIG. 17, the four corners of the film 15, which is rectangular, are grasped by the film grippers 207 and a central portion of the film is grasped at four points by the film pulling mechanisms 211. For stretching the film 15 from the central portion of the film, as shown in FIG. 17, the film pulling mechanisms 211 move outwards crosswise from the central portion of the film 15, while the film grippers 207 move in diagonal directions. As a result, the film 15 whose central portion and four corners are thus grasped at eight points can be stretched by being pulled from its central portion. The pulling operation is performed by actuators Act provided in the film pulling mechanisms 211 and the film grippers 207 (refer FIG. 19), conditions such as pulling speed and pulling quantity differ depending on the properties of the film 15 and the specification of actuators Act.

[0087] It is also possible to provide rotating mechanisms in the film grasping portions of both film pulling mechanisms 211 and film grippers 207 and effect film stretching through the rotating mechanisms. To be more specific, by grasping the film 15 at eight points through the film pulling mechanisms 211 and the film grippers 207 and causing the film grasping portions of the actuators to turn downward.

[0088] After the film 15 grasped at its four corners has thus been stretched by being pulled from its central portion through the film pulling mechanisms 211, the stretched film 15 is applied over the tray 2 and is made integral with the container, whereby there is formed a packaged trays 2, in which the stretched film 15 constitutes a cover portion as is the case with the description of the former embodiment. The process for forming the cover portion of the packaged trays 2 is as follows.

[0089] First, when such a state as shown in FIG. 17 has been attained, the container raising/lowering mechanism of the tray table 3 causes the tray 2 charged with the article to be packaged to rise toward the stretched film 15. It is preferable that the rising speed be 50 mm or so per second.

[0090] Upon contact of the article to be packaged or the opening 121 of the tray 2 with the stretched film 15, the rising speed is decreased to 20 mm or so per second to cover the opening 121 little by little. The opening 121 of the tray 2 is a fitting edge 208. Further, the stretched film 15 is pushed upward with the pressure of the tray 2 of the article to be packaged and the film grippers 207 and the film pulling mechanisms 211 turn slightly, causing the overhanging portions of the film 15 overhanging from the opening 121 to approach the side faces of the tray 2. At this time it is preferable that the film grasping direction of the film grippers 207 and film pulling mechanisms 211 is upward toward the container opening.

[0091] When end portions of the stretched film 15 have arrived at a position lower than the opening 121, blowers 206 positioned within the packaging unit 202 are driven to blow hot air to the four sides of the tray 2, thereby allowing the stretched film 15 to be fitted with the opening 121, whereby a solid edge portion 210 is formed and it is possible to form a packaged trays 2.

[0092] A control system for controlling the above structure of the automatic packaging apparatus 201 is now explained with reference to FIGS. 18 to 25.

[0093] The former embodiment described first has a different packaging manner to the other two former embodiments. The control system described hereafter is suitable for latter two embodiments of the present invention. However, the film unit 205 is commonly used for all former embodiments. Thus, the control system described hereafter is suitable for all former embodiments with respect to a control of the film unit 205.

[0094]FIG. 18 is a functional block diagram showing a control system of the automatic packaging apparatus 201. The automatic packaging apparatus 201 comprises an input/display device 302, whose outer structure is not shown, for inputting driving and packaging condition data and displaying necessary information. The driving and packaging condition data, input by the input/display device 302, are input into an input/display controller 303 to be controlled in the input/display controller 303, so that the driving and packaging condition data are displayed on the input/display device 302. The driving and packaging condition data input by the input/display device 302 are the driving condition data, packaging number of the tray 2 for instance, and the packaging condition data, the thickness and width of the film 15 to be formed by the film unit 205 for instance.

[0095] The input/display controller 303 transmits the input driving and packaging condition data into an information inputting controller 304. The information inputting controller 304 transmits the input driving and packaging condition data into an packaging condition setting controller 305. The packaging condition setting controller 305 refers a packaging condition data base 306 to obtain setting condition of each portion corresponding to the input packaging condition data. The packaging condition data are the data, for instance, data for diving the motor 32, the motor M in FIG. 19, of the film unit 205 so as to limit the thickness of the film 15 corresponding to the input thickness data as packaging condition data, and data for driving the actuator Act of the film unit 205 so as to form the film having the width corresponding to the input width data as packaging condition data and so on. The packaging condition setting controller 305 transmits the obtained packaging condition data to a packaging controller 307 and the film forming controller 301 which controls each portions of the film unit 205.

[0096] The film forming controller 301 transmits the packaging condition data into the input/display controller 303 according to transmittal request from the input/display controller 303. The input/display controller 303 converts the packaging condition data to readable information for operators to display the same on the input by the input/display device 302.

[0097] The packaging controller 307 transmits a film forming start-up signal into the film forming controller 301, when the packaging condition data was transmitted from the packaging condition setting controller 305, on condition that the packaging controller 307 was received a tray detecting signal, which identifies tray supply into the tray feed unit 203, from a tray unit 308. The film forming controller 301 drives the extruding unit 101 and the film forming unit 4 according to the film forming start-up signal, causing the extruding unit 101 and the film forming unit 4 to start up. As to following film forming operation and packaging operation, explanations thereof are here omitted because these operations are described above. As to data processing for film forming operation and packaging operation will be explained below.

[0098]FIG. 19 is a block diagram showing the control system for executing data processing with respect to the operation shown in FIG. 18. Each portion 301, 303, 304, 305, 307 and 308 shown in functional diagram of FIG. 18 identify a microcomputer comprises a CPU (central processing unit) 401, RAM (random access memory) 402 and ROM (read-only memory) 403. The microcomputer controls peripheral devices by processing of the CPU 401 according to operating program and application program stored in the ROM 403. As to a recording medium for storing the operating program and the application program, it may be used, for instance, the ROM 403, a hard disk drive (HDD) 404 connected to the CPU 401, MO (magnetic optical disk), DVD-ROM (digital video disk), DVD-RAM (digital video disk) and so on. The HDD 404 stores the packaging condition data base 306 shown in FIG. 18. The peripheral devices is driven by control of the each portion 301, 303, 304, 305, 307 and 308, shown in functional diagram of FIG. 18, according to the operating program and the application program stored in the recording medium, so as to execute the film forming operation and the packaging operation.

[0099] The microcomputer, comprises CPU 401, RAM 402 and ROM 403, is connected with each portion provided in the packaging unit 202, a conveyance unit 406 comprising the tray feed unit 203 and the tray discharge unit 204, and film unit 205, via a system bus 405. Each portion connected with the microcomputer identify the actuator Act, the motor M, piezoelectric element 110 and heater 105 provided in the film unit 205, the actuator Act, the heater H and the blower 206 provided in the packaging unit 202, and the motor M and the sensor S provided in the conveyance unit 406.

[0100] FIGS. 20 to 25 are flow charts showing summary of the data processing with respect to the film forming process and the packaging process in the automatic packaging apparatus 201. The data processing of the film forming process and the packaging process is now described with reference to these flow chats.

[0101]FIG. 20 shows main routine executed in the packaging controller 307. First, the packaging controller 307 reads the initial conditions (step S101), and starts up each subroutine (step S102). Then each subroutine shown in FIGS. 21 to 22 is started up.

[0102] The subroutine shown in FIG. 21, executed in the input/display controller 303, determines whether the driving condition is input (step S201), and whether the packaging condition is input (step S203). The input/display controller 303, which determines the driving condition is input and the packaging condition is input, executes setting operation with respect to the input driving condition (step S202) and the input packaging condition (step s204). The subroutine shown in FIG. 23, executed in the packing condition setting controller 305, determines the conditions are input (Y of step S401), so that the packing condition setting controller 305 refers the packaging condition data base 306 stored in the HDD 404 according to the input packaging condition to obtain the setting conditions of each portion, setting each portion according to obtained setting conditions (step S402). The main routine, executed in the packaging controller 307, shown in FIG. 20 executes reading process of setting conditions from the packaging condition setting controller 305 (step S103). Then the packaging controller 307 sets a desired packaging number to “n” (step S104). The desired packaging number is set in counter area presented in work area of the RAM 402. The packaging controller 307 determines whether the tray is present (step S105).

[0103]FIG. 22 is a flow chart showing a subroutine executed in the packaging controller 307. The packaging controller 307 drives the actuator Act to convey the tray 2 certain amount (step S303) and cause the conveyed tray 2 raising (step S304), when the packaging controller 307 was received the tray detecting signal from the feed unit 308 (Y of step S301), on condition that last packaging operation completed (Y of step S302). The packaging controller 307 transmits the film forming start-up signal into the film forming controller 301 (step S305), and waits for a packaging completion signal (step S306). The main routine executed in the packaging controller 307 shown in FIG. 20 determines that the tray is fed according to the film forming start-up signal (Y of step S105). Then the packaging controller 307 increments counter value (step S106). The packaging controller 307 returns the process of step S103 until the counter value will become “n” as desired packaging number set in step S104.

[0104]FIG. 24 is a flow chart showing a subroutine executed in a film forming controller 301. The film forming controller 301 determines whether the film forming start-up signal is received (step S411). The film forming controller 301 starts up the film forming operation (step S412) when the film forming controller 301 is received the film forming start-up signal from the packaging controller 307. The film forming controller 301 drives the piezoelectric element 110 (step S413), just before completion of the film forming operation, to urge smooth separation of the film 15 from the melted resin. Then the film forming controller 301 transmits the film forming completion signal to the CPU 401 after the film forming operation (step S414). The CPU 401 uses the film forming completion signal for the packaging controller 307.

[0105]FIG. 25 is a flow chart showing a subroutine executed in the packaging controller 307. The packaging controller 307 waits for receiving the film forming completion signal transmitted from the film forming controller 301 (step S414 of FIG. 24). The packaging controller 307 drives actuator Act to execute the film grasping operation (step S502), the film moving operation (step S503), and the film stretching operation (step S504) in the successive manner when the packaging controller 307 received the film forming completion signal. Then the packaging controller 307 drives the actuator Act to raise the tray (step S505), and drives the heater H and the blower 206 to heat and shrink the overhanging portion of the film 15 overhung from the opening 121 of the tray 2, so that the solid edge portion 210 is formed at the peripheral of the film 15 (step S506). Thus, the tray 2 charged with the article is packaged with the film 15.

[0106] As next process, the packaging controller 307 transmits the packaging completion signal to the CPU 401 (step S507). Thus, the subroutine for executing the control of the conveyance unit 406 executed in the packaging controller 307 shown in FIG. 22 determines that the packaging completion signal is received (Y of step S306). Then the packaging controller 307 drives the motor M to lower the tray 2 (step S307) and covey the tray 2 with certain amount (step S308).

[0107] Whole process for packaging the tray 2 with the film 15 completes after completion of the operation according to the process of step 308 (refer FIG. 22).

[0108] The main routine shown in FIG. 20 determines that the counter value reaches “n”, so that the packaging controller 307 excutes stop process of the subroutine (step S109), on condition that the last tray 2 is discharged from the tray discharge unit (Y of step S108).

[0109] The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the present invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0110] The present application is based on Japanese Priority Documents hei 11-82942 filed on Mar. 26, 1999 and 2000-079623 filed on Mar. 22, 2000, the content of which are incorporated herein by reference. 

1. An automatic packaging method, comprising the steps of: extruding melted resin material as raw material of a film from a resin extruding outlet; cooling the extruded resin so as to form the film; introducing the film immediately after forming the film above a tray charged with an article to be packaged; and packaging the article with the film.
 2. An automatic packaging method, comprising the steps of: positioning a tray, which contains an article to be packaged, adjacent to a film extruding mechanism for extruding melted resin material as raw material of a film from a resin extruding outlet so as to form the film; and packaging the article with the film while the film extruding mechanism forts the film.
 3. An automatic packaging method according to claim 1, wherein a space of the resin extruding outlet is adjusted before extruding melted resin material so as to adjusting the thickness of film to be formed.
 4. An automatic packaging method according to claim 2, wherein a space of the resin extruding outlet is adjusted before extruding melted resin material so as to adjusting the thickness of film to be formed.
 5. An automatic packaging method according to claim 1 or 2, wherein a width of the resin extruding outlet is adjusted before extruding melted resin material so as to adjusting the width of film to be formed.
 6. An automatic packaging method according to claim 3 or 4, wherein a width of the resin extruding outlet is adjusted before extruding melted resin material so as to adjusting the width of film to be formed.
 7. An automatic packaging method according to claim 1, wherein the extruded resin is touched with a surface of rotating cooling drum so as to cool the extruded resin from the resin extruding outlet.
 8. An automatic packaging method according to claim 2, wherein the extruded resin is touched with a surface of rotating cooling drum so as to cool the extruded resin from the resin extruding outlet.
 9. An automatic packaging method according to claims 7 or 8, wherein the rotating velocity of the cooling drum is adjusted according to the thickness of film to be formed.
 10. An automatic packaging apparatus, comprising: a film extruding mechanism for extruding melted resin material as raw material of a film from a resin extruding outlet; a film forming mechanism for touching the extruded resin with a surface of rotating cooling drum so as to cool and solidify the extruded resin from the resin extruding outlet; and a packaging mechanism for introducing the film immediately, after solidifying on the surface of cooling drum, above a tray charged with an article to be packaged to package the article with the film.
 11. An automatic packaging apparatus according to claim 10, wherein size of the resin extruding outlet is adjustable.
 12. An automatic packaging apparatus according to claim 10, further comprising an obstructing plate disposed at the resin extruding outlet with whole width thereof, the obstructing plate is capable of moving so as to adjust a space of the resin extruding outlet so that the obstructing plate adjusts extruding amount of the melted resin from the resin extruding outlet so as to control the thickness of the film to be formed.
 13. An automatic packaging apparatus according to claim 10, further comprising a pair of obstructing members disposed at the resin extruding outlet so as to the ends of the obstructing members are opposite, the obstructing members are capable of sliding so as to adjust a width of the resin extruding outlet so that the obstructing members adjust the width of the melted resin from the resin extruding outlet so as to control the width of the film to be formed.
 14. An automatic packaging apparatus according to claim 10, wherein the resin extruding outlet is positioned higher than the axis of the cooling drum, and the resin extruding outlet is arranged upward.
 15. An automatic packaging apparatus according to claim 10, wherein the cooling drum is thin cylinder having at least one hollow supporting shaft connected with a pipe via a rotary joint so as to introduce the coolant into the cooling drum.
 16. An automatic packaging apparatus according to claim 10, wherein a surface of the cooling drum has fluoro resin treatment.
 17. An automatic packaging apparatus according to claim 10, wherein rotation velocity of the cooling drum is adjustable.
 18. An automatic packaging apparatus according to claim 10, wherein a film extruding mechanism having the resin extruding outlet and a film forming mechanism having the cooling drum is attached uniformly on a supporting frame, and further comprising a raising/lowering mechanism for rising or lowering the supporting frame toward the tray charged with the article to be packaged.
 19. An automatic packaging apparatus according to claim 10, further comprising a scraper whose edge is positioned upward so as to touch the cooling drum or be disposed toward the cooling drum with little gap.
 20. An automatic packaging apparatus according to claim 19, wherein the scraper is driven so as to generate micro-vibration. 